• Molecules and Cells
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• 제42권11호
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• pp.763-772
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• 2019

Periodontitis is characterized by the loss of periodontal tissues, especially alveolar bone. Common therapies cannot satisfactorily recover lost alveolar bone. Periodontal ligament stem cells (PDLSCs) possess the capacity of self-renewal and multilineage differentiation and are likely to recover lost alveolar bone. In addition, periodontitis is accompanied by hypoxia, and hypoxia-inducible $factor-1{\alpha}$ ($HIF-1{\alpha}$) is a master transcription factor in the response to hypoxia. Thus, we aimed to ascertain how hypoxia affects runt-related transcription factor 2 (RUNX2), a key osteogenic marker, in the osteogenesis of PDLSCs. In this study, we found that hypoxia enhanced the protein expression of $HIF-1{\alpha}$, vascular endothelial growth factor (VEGF), and RUNX2 ex vivo and in situ. VEGF is a target gene of $HIF-1{\alpha}$, and the increased expression of VEGF and RUNX2 proteins was enhanced by cobalt chloride ($CoCl_2$, $100{\mu}mol/L$), an agonist of $HIF-1{\alpha}$, and suppressed by 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1, $10{\mu}mol/L$), an antagonist of $HIF-1{\alpha}$. In addition, VEGF could regulate the expression of RUNX2, as RUNX2 expression was enhanced by human VEGF ($hVEGF_{165}$) and suppressed by VEGF siRNA. In addition, knocking down VEGF could decrease the expression of osteogenesis-related genes, i.e., RUNX2, alkaline phosphatase (ALP), and type I collagen (COL1), and hypoxia could enhance the expression of ALP, COL1, and osteocalcin (OCN) in the early stage of osteogenesis of PDLSCs. Taken together, our results showed that hypoxia could mediate the expression of RUNX2 in PDLSCs via $HIF-1{\alpha}$-induced VEGF and play a positive role in the early stage of osteogenesis of PDLSCs.

• 한국산학기술학회논문지
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• 제22권4호
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• pp.353-359
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• 2021

군은 군사훈련을 실전적으로 수행하기 위하여 최신 과학기술을 적용한 마일즈 장비를 활용한 훈련체계를 구축하고 있다. 마일즈 훈련체계는 마일즈 장비를 활용하여 야전에서 실기동 훈련을 실시함으로써 전투 인원과 장비의 피해상황을 실제 전장과 동일하게 모사할 수 있도록 하는 체계이다. 이를 통해 훈련병력은 실전과 유사한 체험을 할 수 있으며 특히, 정보, 통신 및 컴퓨터 시뮬레이션 등의 첨단 과학기술을 활용하는 통합체계로 구축되어 훈련에 참가하는 용사들의 훈련효과를 극대화 할 수 있다. 본 연구는 육군에서 활용 중인 마일즈 훈련효과를 과학적 기법을 활용하여 분석하였으며 중대급 마일즈를 대상으로 하였다. 특히 훈련효과를 분석하기 위한 효과지표는 관련 문헌조사 및 전문가 의견수렴을 통해 도출하였으며 Swing기법을 적용하여 효과지표별 가중치를 산출하고 훈련 경험자를 대상으로 한 설문조사 결과를 결합하여 최종 훈련효과를 도출하였다. 연구결과 마일즈 훈련효과는 기존의 마일즈를 활용하지 않는 훈련에 비해 2.6배 효과적이며 분산분석을 통해 신분별로 마일즈 훈련에 대한 만족도는 높으며 그 차이는 통계적으로 유의미한 것으로 도출되었다.

• 한국산학기술학회논문지
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• 제22권4호
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• pp.345-352
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• 2021

육군은 교육훈련 효과를 향상시키기 위해 노력을 경주하고 있다. 그러나 실제 훈련 시 많은 제한사항으로 인해 실전적인 교육훈련이 제한된다. 이러한 제한사항을 극복하기 위해 가상현실 기술을 활용하고 있다. 가상현실 기술은 다양한 유형으로 발전하고 있으며, 육군은 비용 대 교육효과를 고려하여 가상현실 훈련체계를 도입할 필요가 있다. 육군은 실제 장비와 유사하게 제작된 고비용의 시뮬레이터형을 주로 사용하고 있다. 최근에는 HMD(Head Mounted Display, 이하 HMD)를 착용한 저비용의 몰입형 가상현실 훈련체계도 사용 중이다. 본 연구는 육군 방공학교에서 운영중인 시뮬레이터형과 몰입형 가상현실 훈련체계에 대한 비용 대 교육효과를 분석한다. 연구 방법은 첫 번째, 계층적 분석기법(AHP : Analytic Hierarchy Process, 이하 AHP)으로 교육효과를 분석한다. 두 번째, 비용은 가상현실 훈련체계의 제작 비용을 적용하여 비용 대 교육효과를 분석한다. 분석결과, 비용 대 교육효과는 몰입형이 시뮬레이터형보다 3.4배 높은 것으로 확인되었다. 이번 연구결과를 통해 가상현실 훈련체계의 비용 대 교육효과 분석을 위한 기초자료로 활용이 가능 할 것이다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권2호
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• pp.141-149
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• 2011

Environment Conversion Factors, which are stipulated in System Reliability Toolkit, have a lot of advantages once applied in a reliability data handbook such as NPRD-95, during the process of reliability prediction. However, the factors have a restriction in their applications because they don't deal with a few environments, e.g., Missile Launch (ML). In this study, environment factors of various components from MIL-HDBK-217F were analyzed to address this problem. Statistical computations showed that converting from Airborne Rotary Wing (ARW) to Missile Launch (ML) was the most coherent by comparing coefficient of determination. In addition, conversion factors from System Reliability Toolkit and those from the statistical calculations were evaluated in terms of their similarities.

• Current Optics and Photonics
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• 제3권6호
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• pp.502-509
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• 2019

Based on the typical pixel structure and parameters of a polysilicon uncooled bolometer, the absorption rate of a polysilicon microbridge infrared detector for 10.6 ㎛ laser energy was calculated through the optical admittance method, and the thermal coupling model of a polysilicon microbridge component irradiated by far infrared laser was established based on theoretical formulas. Then a numerical simulation study was carried out by means of finite element analysis for the actual working environment. It was found that the maximum temperature and maximum stress of the microbridge component are approximately exponentially changing with the laser power of the irradiation respectively and that they increase monotonically. The highest temperature zone of the model is gradually spread by the two corners of the bridge surface that are not connected to the bridge legs, and the maximum stress acts on both sides of the junction of the microbridge legs and the substrate. The mechanism of laser-induced hard damage to polysilicon detectors is the melting damage caused by high temperature. This paper lays the foundation for the subsequent study of the interference mechanism of the laser on working state polysilicon detectors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권3호
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• pp.1065-1085
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• 2020

With rapid growth of content demands, device-to-device (D2D) content sharing is exploited to effectively improve the service quality of users. Considering the limited storage space and various content demands of users, caching schemes are significant. However, most of them ignore the influence of the asynchronous content reuse and the selfishness of users. In this work, the user preferences are defined by exploiting the user-oriented content popularity and the current caching situation, and further, we propose the social-aware rate, which comprehensively reflects the achievable contents download rate affected by the social ties, the caching indicators, and the user preferences. Guided by this, we model the collaborative caching problem by making a trade-off between the redundancy of caching contents and the cache hit ratio, with the goal of maximizing the sum of social-aware rate over the constraint of limited storage space. Due to its intractability, it is computationally reduced to the maximization of a monotone submodular function, subject to a matroid constraint. Subsequently, two social-aware collaborative caching algorithms are designed by leveraging the standard and continuous greedy algorithms respectively, which are proved to achieve different approximation ratios in unequal polynomial-time. We present the simulation results to illustrate the performance of our schemes.

• 한국안전학회지
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• 제28권4호
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• pp.103-106
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• 2013

During a military service, noise has unusual characteristics, and constitutes a serious hazard to hearing of military servicemen. The purpose of this study is to understand the use of hearing protection and to assess the safety effects of hearing protection by using a ear plug in military. A total of 208(the army : 101, an air force : 107) serviceman were studied utilizing a questionnaire to know how many serviceman use the hearing protection and a total of 202(the army : 110, an air force : 92) serviceman were also studied using a ear fit validation device to assess the safety effects of hearing protection by using a ear plug. The results showed that the army have low used of hearing protection than an air force because of the low frequency of the noise exposure in the army. Personal attenuation rate was increased with 8 dB after fitting education. Therefore, it is recommended that use of proper hearing protection and fitting education was more suitable for military servicemen who were being exposed of the noise in domestic military.

• 한국통신학회논문지
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• 제33권10B호
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• pp.904-910
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• 2008

본 논문에서는 군의 요구사항을 고려하여 군 통신망의 서비스와 관련 파라미터들을 연구하고, u-Army 실험망을 시뮬레이션을 통해 성능 측정을 하였다. 이를 바탕으로 전 군에 VoIP를 적용할 수 있는 VoIP 설계 가이드라인을 제시하였다. 측정은 패킷과 콜 시그널링 관점에서 지연과 손실에 관하여 몇 가지 시나리오에 대해 측정하였다. 첫 번째는 독립적인 네트워크 서비스에 따라 만족하는 요구사항을 측정하였다. 두 번째는 통합 서비스에서 지연과 손실에 관하여 백그라운드 트래픽을 증가시키면서 그 결과를 측정하였다. 마지막으로 시뮬레이션에 근거하여 IP PBX 장비의 설치 위치에 따라 네트워크의 구성을 분류하여 설계 가이드라인을 제시하였으며, 현재 군의 고정된 링크의 상황에 맞추어 VoIP 단말기의 수를 정할 수 있도록 계산 방법을 제시하였다.

• 대한핵의학회지
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• 제2권1호
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• pp.59-66
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• 1968

Technetium 99m pertechnetate brain scanning were performed in 3 cases of head injury (2 chronic subdural hematomas and 1 acute epidural hematoma), 2 cases of brain abscess and I case of intracerebral hematoma associated with arteriovenous anomaly. In all the cases brain scintigrams showed "hot areas." Literatures on radioisotope scanning of intracranial lesions were briefly reviewed. With the improvement of radioisotope scanner and development of new radiopharmaceuticals brain scanning became a safe and useful screening test for diagnosis of intracranial lesions. Brain scanning can be easily performed even to a moribund patient without any discomfort and risk to the patient which are associated with cerebral angiography or pneumoencephalography. Brain scanning has been useful in diagnosis of brain tumor, brain abscess, subdural hematoma, and cerebral vascular diseases. In 80 to 90% of brain tumors positive scintigrams can be expected. Early studies were done with $^{203}Hg$-Neohydrin or $^{131}I$-serum albumin. With these agents, however, patients receive rather much radiation to the whole body and kidneys. In 1965 Harper introduced $^{99m}Tc$ to reduce radiation dose to the patient and improve statistical variation in isotope scanning.

• Current Optics and Photonics
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• 제4권3호
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• pp.210-220
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• 2020

Aiming at the problem that the Local Sparse Difference Index algorithm has low accuracy and low efficiency when detecting target anomalies in a hyperspectral image, this paper proposes a Weighted Collaborative Representation and Sparse Difference-Based Hyperspectral Anomaly Detection algorithm, to improve detection accuracy for a hyperspectral image. First, the band subspace is divided according to the band correlation coefficient, which avoids the situation in which there are multiple solutions of the sparse coefficient vector caused by too many bands. Then, the appropriate double-window model is selected, and the background dictionary constructed and weighted according to Euclidean distance, which reduces the influence of mixing anomalous components of the background on the solution of the sparse coefficient vector. Finally, the sparse coefficient vector is solved by the collaborative representation method, and the sparse difference index is calculated to complete the anomaly detection. To prove the effectiveness, the proposed algorithm is compared with the RX, LRX, and LSD algorithms in simulating and analyzing two AVIRIS hyperspectral images. The results show that the proposed algorithm has higher accuracy and a lower false-alarm rate, and yields better results.